AspNetWebStack/src/System.Web.Mvc/ExpressionUtil/HashCodeCombiner.cs at master · develop9797/AspNetWebStack · GitHub

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// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System.Collections;

namespace System.Web.Mvc.ExpressionUtil
{
    // based on System.Web.Util.HashCodeCombiner
    internal class HashCodeCombiner
    {
        private long _combinedHash64 = 0x1505L;

        public int CombinedHash
        {
            get { return _combinedHash64.GetHashCode(); }
        }

        public void AddFingerprint(ExpressionFingerprint fingerprint)
        {
            if (fingerprint != null)
            {
                fingerprint.AddToHashCodeCombiner(this);
            }
            else
            {
                AddInt32(0);
            }
        }

        public void AddEnumerable(IEnumerable e)
        {
            if (e == null)
            {
                AddInt32(0);
            }
            else
            {
                int count = 0;
                foreach (object o in e)
                {
                    AddObject(o);
                    count++;
                }
                AddInt32(count);
            }
        }

        public void AddInt32(int i)
        {
            _combinedHash64 = ((_combinedHash64 << 5) + _combinedHash64) ^ i;
        }

        public void AddObject(object o)
        {
            int hashCode = (o != null) ? o.GetHashCode() : 0;
            AddInt32(hashCode);
        }
    }
}